package egovframework.com.utl.fcc.service;

import java.io.Serializable;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * 
 * A class that represents an immutable universally unique identifier (UUID). A
 * UUID represents a 128-bit value.
 * 
 * <p>
 * There exist different variants of these global identifiers. The methods of
 * this class are for manipulating the Leach-Salz variant, although the
 * constructors allow the creation of any variant of UUID (described below).
 * 
 * <p>
 * The layout of a variant 2 (Leach-Salz) UUID is as follows:
 * 
 * The most significant long consists of the following unsigned fields:
 * 
 * <pre>
 *   0xFFFFFFFF00000000 time_low
 *   0x00000000FFFF0000 time_mid
 *   0x000000000000F000 version
 *   0x0000000000000FFF time_hi
 * </pre>
 * 
 * The least significant long consists of the following unsigned fields:
 * 
 * <pre>
 *   0xC000000000000000 variant
 *   0x3FFF000000000000 clock_seq
 *   0x0000FFFFFFFFFFFF node
 * </pre>
 * 
 * <p>
 * The variant field contains a value which identifies the layout of the
 * <tt>UUID</tt>. The bit layout described above is valid only for a
 * <tt>UUID</tt> with a variant value of 2, which indicates the Leach-Salz
 * variant.
 * 
 * <p>
 * The version field holds a value that describes the type of this <tt>UUID</tt>
 * . There are four different basic types of UUIDs: time-based, DCE security,
 * name-based, and randomly generated UUIDs. These types have a version value of
 * 1, 2, 3 and 4, respectively.
 * 
 * <p>
 * For more information including algorithms used to create <tt>UUID</tt>s, see
 * the Internet-Draft <a
 * href="http://www.ietf.org/internet-drafts/draft-mealling-uuid-urn-03.txt"
 * >UUIDs and GUIDs</a> or the standards body definition at <a
 * href="http://www.iso.ch/cate/d2229.html">ISO/IEC 11578:1996</a>.
 * 
 * @version 1.14, 07/12/04
 * @since 1.5
 */
@SuppressWarnings("serial")
public class EgovFormBasedUUID implements Serializable {
	/** Returns val represented by the specified number of hex digits. */
	private static String digits(long val, int digits) {
		long hi = 1L << (digits * 4);
		return Long.toHexString(hi | (val & (hi - 1))).substring(1);
	}

	/**
	 * Creates a <tt>UUID</tt> from the string standard representation as
	 * described in the {@link #toString} method.
	 * 
	 * @param name
	 *            a string that specifies a <tt>UUID</tt>.
	 * @return a <tt>UUID</tt> with the specified value.
	 * @throws IllegalArgumentException
	 *             if name does not conform to the string representation as
	 *             described in {@link #toString}.
	 */
	public static EgovFormBasedUUID fromString(String name) {
		String[] components = name.split("-");
		if (components.length != 5)
			throw new IllegalArgumentException("Invalid UUID string: " + name);
		for (int i = 0; i < 5; i++)
			components[i] = "0x" + components[i];

		long mostSigBits = Long.decode(components[0]).longValue();
		mostSigBits <<= 16;
		mostSigBits |= Long.decode(components[1]).longValue();
		mostSigBits <<= 16;
		mostSigBits |= Long.decode(components[2]).longValue();

		long leastSigBits = Long.decode(components[3]).longValue();
		leastSigBits <<= 48;
		leastSigBits |= Long.decode(components[4]).longValue();

		return new EgovFormBasedUUID(mostSigBits, leastSigBits);
	}

	/*
	 * The most significant 64 bits of this UUID.
	 * 
	 * @serial
	 */
	private final long mostSigBits;

	/*
	 * The least significant 64 bits of this UUID.
	 * 
	 * @serial
	 */
	private final long leastSigBits;

	/*
	 * The version number associated with this UUID. Computed on demand.
	 */
	private transient int version = -1;

	/*
	 * The variant number associated with this UUID. Computed on demand.
	 */
	private transient int variant = -1;

	/*
	 * The timestamp associated with this UUID. Computed on demand.
	 */
	private transient volatile long timestamp = -1;

	/*
	 * The clock sequence associated with this UUID. Computed on demand.
	 */
	private transient int sequence = -1;

	/*
	 * The node number associated with this UUID. Computed on demand.
	 */
	private transient long node = -1;

	// Constructors and Factories

	/*
	 * The hashcode of this UUID. Computed on demand.
	 */
	private transient int hashCode = -1;

	/*
	 * The random number generator used by this class to create random based
	 * UUIDs.
	 */
	private static volatile SecureRandom numberGenerator = null;

	/**
	 * Static factory to retrieve a type 3 (name based) <tt>UUID</tt> based on
	 * the specified byte array.
	 * 
	 * @param name
	 *            a byte array to be used to construct a <tt>UUID</tt>.
	 * @return a <tt>UUID</tt> generated from the specified array.
	 */
	public static EgovFormBasedUUID nameUUIDFromBytes(byte[] name) {
		MessageDigest md;
		try {
			// 2011.10.10 보안점검 후속조치 암호화 알고리즘 변경(MD5 -> SHA-256)
			// md = MessageDigest.getInstance("MD5");
			md = MessageDigest.getInstance("SHA-256");
		} catch (NoSuchAlgorithmException nsae) {
			// throw new InternalError("MD5 not supported");
			throw new InternalError("SHA-256 not supported");
		}
		// 2011.10.10 보안점검 후속조치
		if (md == null) {
			throw new RuntimeException("MessageDigest is null!!");
		}
		byte[] sha = md.digest(name);
		byte[] md5Bytes = new byte[8];
		System.arraycopy(sha, 0, md5Bytes, 0, 8);
		// 2011.10.10 보안점검 후속조치 끝

		md5Bytes[6] &= 0x0f; /* clear version */
		md5Bytes[6] |= 0x30; /* set to version 3 */
		md5Bytes[8] &= 0x3f; /* clear variant */
		md5Bytes[8] |= 0x80; /* set to IETF variant */

		return new EgovFormBasedUUID(md5Bytes);
	}

	/**
	 * Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
	 * 
	 * The <code>UUID</code> is generated using a cryptographically strong
	 * pseudo random number generator.
	 * 
	 * @return a randomly generated <tt>UUID</tt>.
	 */
	public static EgovFormBasedUUID randomUUID() {
		SecureRandom ng = numberGenerator;
		if (ng == null) {
			numberGenerator = ng = new SecureRandom();
		}

		byte[] randomBytes = new byte[16];
		ng.nextBytes(randomBytes);
		randomBytes[6] &= 0x0f; /* clear version */
		randomBytes[6] |= 0x40; /* set to version 4 */
		randomBytes[8] &= 0x3f; /* clear variant */
		randomBytes[8] |= 0x80; /* set to IETF variant */

		return new EgovFormBasedUUID(randomBytes);
	}

	/*
	 * Private constructor which uses a byte array to construct the new UUID.
	 */
	private EgovFormBasedUUID(byte[] data) {
		long msb = 0;
		long lsb = 0;
		for (int i = 0; i < 8; i++)
			msb = (msb << 8) | (data[i] & 0xff);
		for (int i = 8; i < 16; i++)
			lsb = (lsb << 8) | (data[i] & 0xff);
		this.mostSigBits = msb;
		this.leastSigBits = lsb;
	}

	// Field Accessor Methods

	/**
	 * Constructs a new <tt>UUID</tt> using the specified data.
	 * <tt>mostSigBits</tt> is used for the most significant 64 bits of the
	 * <tt>UUID</tt> and <tt>leastSigBits</tt> becomes the least significant 64
	 * bits of the <tt>UUID</tt>.
	 * 
	 * @param mostSigBits
	 * @param leastSigBits
	 */
	public EgovFormBasedUUID(long mostSigBits, long leastSigBits) {
		this.mostSigBits = mostSigBits;
		this.leastSigBits = leastSigBits;
	}

	/**
	 * The clock sequence value associated with this UUID.
	 * 
	 * <p>
	 * The 14 bit clock sequence value is constructed from the clock sequence
	 * field of this UUID. The clock sequence field is used to guarantee
	 * temporal uniqueness in a time-based UUID.
	 * <p>
	 * 
	 * The clockSequence value is only meaningful in a time-based UUID, which
	 * has version type 1. If this UUID is not a time-based UUID then this
	 * method throws UnsupportedOperationException.
	 * 
	 * @return the clock sequence of this <tt>UUID</tt>.
	 * @throws UnsupportedOperationException
	 *             if this UUID is not a version 1 UUID.
	 */
	public int clockSequence() {
		if (version() != 1) {
			throw new UnsupportedOperationException("Not a time-based UUID");
		}
		if (sequence < 0) {
			sequence = (int) ((leastSigBits & 0x3FFF000000000000L) >>> 48);
		}
		return sequence;
	}

	/**
	 * Compares this UUID with the specified UUID.
	 * 
	 * <p>
	 * The first of two UUIDs follows the second if the most significant field
	 * in which the UUIDs differ is greater for the first UUID.
	 * 
	 * @param val
	 *            <tt>UUID</tt> to which this <tt>UUID</tt> is to be compared.
	 * @return -1, 0 or 1 as this <tt>UUID</tt> is less than, equal to, or
	 *         greater than <tt>val</tt>.
	 */
	public int compareTo(EgovFormBasedUUID val) {
		// The ordering is intentionally set up so that the UUIDs
		// can simply be numerically compared as two numbers
		return (this.mostSigBits < val.mostSigBits ? -1
				: (this.mostSigBits > val.mostSigBits ? 1
						: (this.leastSigBits < val.leastSigBits ? -1
								: (this.leastSigBits > val.leastSigBits ? 1 : 0))));
	}

	/**
	 * Compares this object to the specified object. The result is <tt>true</tt>
	 * if and only if the argument is not <tt>null</tt>, is a <tt>UUID</tt>
	 * object, has the same variant, and contains the same value, bit for bit,
	 * as this <tt>UUID</tt>.
	 * 
	 * @param obj
	 *            the object to compare with.
	 * @return <code>true</code> if the objects are the same; <code>false</code>
	 *         otherwise.
	 */
	@Override
	public boolean equals(Object obj) {
		// 보안 취약점 점검 지적사항 반영 시작
		if (obj == null)
			return false;
		// 보안 취약점 점검 지적사항 반영 시작 끝
		if (!(obj instanceof EgovFormBasedUUID))
			return false;
		if (((EgovFormBasedUUID) obj).variant() != this.variant())
			return false;
		EgovFormBasedUUID id = (EgovFormBasedUUID) obj;
		return (mostSigBits == id.mostSigBits && leastSigBits == id.leastSigBits);
	}

	/**
	 * Returns the least significant 64 bits of this UUID's 128 bit value.
	 * 
	 * @return the least significant 64 bits of this UUID's 128 bit value.
	 */
	public long getLeastSignificantBits() {
		return leastSigBits;
	}

	/**
	 * Returns the most significant 64 bits of this UUID's 128 bit value.
	 * 
	 * @return the most significant 64 bits of this UUID's 128 bit value.
	 */
	public long getMostSignificantBits() {
		return mostSigBits;
	}

	/**
	 * Returns a hash code for this <code>UUID</code>.
	 * 
	 * @return a hash code value for this <tt>UUID</tt>.
	 */
	@Override
	public int hashCode() {
		if (hashCode == -1) {
			hashCode = (int) ((mostSigBits >> 32) ^ mostSigBits
					^ (leastSigBits >> 32) ^ leastSigBits);
		}
		return hashCode;
	}

	// Object Inherited Methods

	/**
	 * The node value associated with this UUID.
	 * 
	 * <p>
	 * The 48 bit node value is constructed from the node field of this UUID.
	 * This field is intended to hold the IEEE 802 address of the machine that
	 * generated this UUID to guarantee spatial uniqueness.
	 * <p>
	 * 
	 * The node value is only meaningful in a time-based UUID, which has version
	 * type 1. If this UUID is not a time-based UUID then this method throws
	 * UnsupportedOperationException.
	 * 
	 * @return the node value of this <tt>UUID</tt>.
	 * @throws UnsupportedOperationException
	 *             if this UUID is not a version 1 UUID.
	 */
	public long node() {
		if (version() != 1) {
			throw new UnsupportedOperationException("Not a time-based UUID");
		}
		if (node < 0) {
			node = leastSigBits & 0x0000FFFFFFFFFFFFL;
		}
		return node;
	}

	/**
	 * Reconstitute the <tt>UUID</tt> instance from a stream (that is,
	 * deserialize it). This is necessary to set the transient fields to their
	 * correct uninitialized value so they will be recomputed on demand.
	 */
	private void readObject(java.io.ObjectInputStream in)
			throws java.io.IOException, ClassNotFoundException {

		in.defaultReadObject();

		// Set "cached computation" fields to their initial values
		version = -1;
		variant = -1;
		timestamp = -1;
		sequence = -1;
		node = -1;
		hashCode = -1;
	}

	/**
	 * The timestamp value associated with this UUID.
	 * 
	 * <p>
	 * The 60 bit timestamp value is constructed from the time_low, time_mid,
	 * and time_hi fields of this <tt>UUID</tt>. The resulting timestamp is
	 * measured in 100-nanosecond units since midnight, October 15, 1582 UTC.
	 * <p>
	 * 
	 * The timestamp value is only meaningful in a time-based UUID, which has
	 * version type 1. If this <tt>UUID</tt> is not a time-based UUID then this
	 * method throws UnsupportedOperationException.
	 * 
	 * @throws UnsupportedOperationException
	 *             if this UUID is not a version 1 UUID.
	 */
	public long timestamp() {
		if (version() != 1) {
			throw new UnsupportedOperationException("Not a time-based UUID");
		}
		long result = timestamp;
		if (result < 0) {
			result = (mostSigBits & 0x0000000000000FFFL) << 48;
			result |= ((mostSigBits >> 16) & 0xFFFFL) << 32;
			result |= mostSigBits >>> 32;
			timestamp = result;
		}
		return result;
	}

	/**
	 * Returns a <code>String</code> object representing this <code>UUID</code>.
	 * 
	 * <p>
	 * The UUID string representation is as described by this BNF :
	 * 
	 * <pre>
	 *    UUID                   = &lt;time_low&gt; &quot;-&quot; &lt;time_mid&gt; &quot;-&quot;
	 *                             &lt;time_high_and_version&gt; &quot;-&quot;
	 *                             &lt;variant_and_sequence&gt; &quot;-&quot;
	 *                             &lt;node&gt;
	 *    time_low               = 4*&lt;hexOctet&gt;
	 *    time_mid               = 2*&lt;hexOctet&gt;
	 *    time_high_and_version  = 2*&lt;hexOctet&gt;
	 *    variant_and_sequence   = 2*&lt;hexOctet&gt;
	 *    node                   = 6*&lt;hexOctet&gt;
	 *    hexOctet               = &lt;hexDigit&gt;&lt;hexDigit&gt;
	 *    hexDigit               =
	 *          &quot;0&quot; | &quot;1&quot; | &quot;2&quot; | &quot;3&quot; | &quot;4&quot; | &quot;5&quot; | &quot;6&quot; | &quot;7&quot; | &quot;8&quot; | &quot;9&quot;
	 *          | &quot;a&quot; | &quot;b&quot; | &quot;c&quot; | &quot;d&quot; | &quot;e&quot; | &quot;f&quot;
	 *          | &quot;A&quot; | &quot;B&quot; | &quot;C&quot; | &quot;D&quot; | &quot;E&quot; | &quot;F&quot;
	 * </pre>
	 * 
	 * @return a string representation of this <tt>UUID</tt>.
	 */
	@Override
	public String toString() {
		return (digits(mostSigBits >> 32, 8) + "-"
				+ digits(mostSigBits >> 16, 4) + "-" + digits(mostSigBits, 4)
				+ "-" + digits(leastSigBits >> 48, 4) + "-" + digits(
					leastSigBits, 12));
	}

	// Comparison Operations

	/**
	 * The variant number associated with this <tt>UUID</tt>. The variant number
	 * describes the layout of the <tt>UUID</tt>.
	 * 
	 * The variant number has the following meaning:
	 * <p>
	 * <ul>
	 * <li>0 Reserved for NCS backward compatibility
	 * <li>2 The Leach-Salz variant (used by this class)
	 * <li>6 Reserved, Microsoft Corporation backward compatibility
	 * <li>7 Reserved for future definition
	 * </ul>
	 * 
	 * @return the variant number of this <tt>UUID</tt>.
	 */
	public int variant() {
		if (variant < 0) {
			// This field is composed of a varying number of bits
			if ((leastSigBits >>> 63) == 0) {
				variant = 0;
			} else if ((leastSigBits >>> 62) == 2) {
				variant = 2;
			} else {
				variant = (int) (leastSigBits >>> 61);
			}
		}
		return variant;
	}

	/**
	 * The version number associated with this <tt>UUID</tt>. The version number
	 * describes how this <tt>UUID</tt> was generated.
	 * 
	 * The version number has the following meaning:
	 * <p>
	 * <ul>
	 * <li>1 Time-based UUID
	 * <li>2 DCE security UUID
	 * <li>3 Name-based UUID
	 * <li>4 Randomly generated UUID
	 * </ul>
	 * 
	 * @return the version number of this <tt>UUID</tt>.
	 */
	public int version() {
		if (version < 0) {
			// Version is bits masked by 0x000000000000F000 in MS long
			version = (int) ((mostSigBits >> 12) & 0x0f);
		}
		return version;
	}
}